This application claims the benefit of Japanese Patent Application No. 2004-34016 filed Feb. 10, 2004, the entirety of which is incorporated by reference.
1. Field of the Invention
The present invention relates to an impact driver capable of applying rotation and the intermittent impact operation to an output shaft.
2. Description of the Related Art
An impact driver includes a rotation impact mechanism provided between a motor housed in a housing and an output shaft protruding from the housing so as to transfer a motor torque to the output shaft as well as apply the impact operation to the same in the rotative direction in accordance with increase of a load on the output shaft. For example, Japan Published Unexamined Patent Application No. 2002-273666 discloses a rotation impact mechanism in which a spindle rotated by a motor is connected to a hammer through cam grooves and balls, and an anvil (an output shaft) attachable to and detachable from the hammer in the rotative direction is provided in front of the hammer, whereby rotation of the spindle is transferred to the anvil through the hammer. With this structure, when a load on the anvil exceeds a predetermined value, the hammer moves backward along the cam grooves to temporarily disengage from the anvil, and thereafter it moves forward by a coil spring biased to the front along the cam grooves to reengage with the anvil. By repeating the above operation, it is possible to apply the intermittent impact operation to the anvil in the rotative direction.
The above-described impact driver is generally used for screwing with a screw or a bolt etc. Thus, when it is used for screwing an anchor bolt on a material to be processed like a plaster board etc., a percussion drill is used first for boring and then an impact driver is used to screw the anchor bolt into a processed hole. This means that a user has to handle two separate tools in turn, which are, the percussion drill and the impact driver. Consequently, it is troublesome to exchange tools and therefore usability might be reduced.